\texttt{numpy} and \texttt{scipy} provide many of the essential tools
for digital signal processing. \texttt{scipy.signal} provides basic
tools for digital filter design and filtering (eg Butterworth
filters), a linear systems toolkit, standard waveforms such as square
waves, and saw tooth functions, and some basic wavelet functionality.
\texttt{scipy.fftpack} provides a suite of tools for Fourier domain
analysis, including 1D, 2D, and ND discrete fourier transform and
inverse functions, in addition to other tools such as analytic signal
representations via the Hilbert trasformation (\texttt{numpy.fft} also
provides basic FFT functions). \texttt{pylab} provides Matlab
compatible functions for computing and plotting standard time series
analyses, such as historgrams (\texttt{hist}), auto and cross
correlations (\texttt{acorr} and \texttt{xcorr}), power spectra and
coherence spectra (\texttt{psd}, \texttt{csd}, \texttt{cohere} and
\texttt{specgram}).
